Hot gas engine

ABSTRACT

In a Stirling cycle engine, a compressor pump pumps gas from the engine to a reservoir to decrease engine power. The compressor is of the differential piston type with a free piston with controls alternating the working gas pressure on the two sides of the piston to maintain high and low pressures operating a pump for storing working gas in a reservoir under pressure.

ilnitn fitnten l ntern; 1191 Lundquist Aug, 6, 1974 [54] nor GAS ENGHNE 3,355,881 12/1367 1516:1665 2 /1 53 1 3,397,533 8/1 68 St t [75] Invent E 3 Lumqlmmr 3,466,867 9/1969 83:52:: 60/521 we en [73] Assignee: Forennde Fnhrilrsverlten, Esltilstuna, Primary Examiner-Edgar W. Geoghegan Sweden Assistant Examiner-H. Burks [22] Filed, AW 2 W73 Attorney, Agent, or Firm-Laurence R. Brown [21] Appl. No: 346,940 [57] AHSTRACT in a Stirling cycle engine, a compressor pump pumps gas from the engine to a reservoir to decrease engine [58] g? d 522 power. The compressor is of the differential piston we 0 mm type with a. free piston with controls alternating the Working gas pressure on the two sides of the piston to [56] References (MM maintain high and low pressures operating a pump for UNITED STATES PATENTS storing working gas in a reservoir under pressure. 2,746,241 5/1956 Dros et al. 60/521 2,794,315 6/1957 Meijer 60/521 3 (Jimmy ll Dmwmig nor GAS ENGINE This invention relates to a hot gas engine having power control by varying the mean pressure of the working gas and of the type being provided with a compressor pumping working gas from the engine to a reservoir during decrease of power.

Hitherto the said compressor has been directly driven by moving parts of the engine. This has involved a mechanical-transmission being a source of noise pollution. The invention has for its object to provide an engine having a low level of noise and vibration for the complete engine system. it is also an object to provide an engine having a power control of comparatively simple design which should be easy to give service.

According to the present invention this is obtained thereby that said compressor is a free-piston compressor of differential piston type having a governing device supplying working gas of maximum cycle pressure altemating to one and the other of the two sides of the large piston while simultaneously supplying working gas of minimum cycle pressure to the opposite side of said large piston, the small piston being mounted slidably in a cylinder which is connected to said reservoir and to a working chamber of the engine via non-return valves allowing flow of gas in the direction from the engine to the reservoir.

The invention will be described in more detail, reference being made to the drawing which schematically shows a hot gas engine according to the invention.

The reference numeral 1 designates a cylinder of a hot gas engine and the reference numeral 2 designates a working space in said cylinder. A conduit 3 is leading from the working space 2 to a distributer valve 4. Other conduits 5, 6 and 7 also lead to said valve 4. The conduit connects the valve 4 with a pressure reservoir 8 and contains a non-return valve 9 which allows flow of gas in the conduit 5 only in the direction from the reservoir 8 to the valve 4. A free-piston compressor generally indicated by 10 contains a differential piston 11, 12, 13 consisting of a large piston 11 and a small piston 13 interconnected by a piston rod 12.

The compressor will contain a first working space 14 at the left side of the large piston 11 and a second working space 15 at the right side of the large piston 11. The first working space 14 is connected to a valve generally indicated by 16 via a conduit 17 and the second working space 15 is connected to the valve 16 via a conduit 18. Also connected to the valve 16 are conduits 6' and 6" being branched off from the conduit 6 and contain ing non-return valves 19 and 20 respectively allowing flow in the direction to respectively from the valve 4.

The valve 16 contains two valve sections 21 and 22 and is governed by a solenoid 23 allowing either the one or the other of these sections to be located in the active position i.e. in connection with the conduits 17, 18, 6' and 6" leading to the valve 16.

The solenoid 23 is governed by end position switches 24 and 25 located at the end positions of the large piston 11.

A cylinder space 26 located at the right hand side of the small piston 13 is connected to the reservoir 8 via a conduit 27 containing a non-return valve 28 allowing flow of gas only in the direction into the reservoir 8. The space 26 is also connected to the valve 4 via the conduit 7 containing a non-return valve 29 allowing flow of gas through the conduit 7 in the direction into said space 26 only.

The described system will operate as follows.

in case it is desired to decrease the power of the hot gas engine the valve 4 is moved into a position in which the conduits 3 and 6 are interconnected. The working space 2 of the engine will contain working gas of a cyclically varying pressure. The non-return valves 19 and 20 will now ensure that the conduit 6 between the valve 19 and the valve 16 will contain a gas pressure corresponding to the minimum pressure in the working space 2 while the conduit 6" between the valve 20 and the valve 16 will contain maximum pressure. The said maximum and minimum pressures are conveyed through the conduits 17 and 18 and effect a difference in pressure across the large piston 11. The large piston 11 will now start an oscillating movement as the difference in pressure changes its direction as soon as the piston 1 1 has reached its end positions. Here the piston 11 will activate the end switches 24 and 25 giving signals to the solenoid 23.

In the actual position of the valve 4 the conduits 3 and 7 are also interconnected. Thus the oscillating movement of the smaller piston 13 will cause a pumping of gas from the working space 2 into the reservoir The power of the hot gas engine will decrease with decreasing amount of gas in the working cycle as is well known in the art.

in case it is desired to increase the power output of the engine the valve 4 is moved into a position in which the conduit 3 is connected to the conduit 5. Gas may now flow from the tank 8 containing gas under higher pressure than the prevailing minimum cycle pressure in the working cycle to the working space 2.

What is claimed is:

1. A hot gas engine having a working space with a charge of working gas therein under varying pressure comprising in combination, means pumping working gas from the engine into a reservoir to decrease power comprising a cylinder having a free piston therein, conduit means connecting to opposite sides of said piston working gas from said engine respectively of higher and lower working pressures to cause the piston to move, valve means respnsive to the piston as it nears the end of its movement for alternating the pressures on different sides of the piston causing it to oscillate, and said means pumping gas further comprising pumping structure connected to the piston and to said working chamber to pump working gas into said reservoir by oscillation of said piston, and valve means controlling the flow of working gas to said piston to control the pumping of working gas from said chamber.

2. An engine as defined in claim 1 wherein said conduit means comprises two conduits with oppositely connected non-return valves coupled respectively therein, said conduits being connected between said working chamber and opposite sides of said free piston.

3. An engine as defined in claim 2 wherein the valve means comprises a reversing valve coupled in said two conduits between said working chamber and said piston. 

1. A hot gas engine having a working space with a charge of working gas therein under varying pressure comprising in combination, means pumping working gas from the engine into a reservoir to decrease power comprising a cylinder having a free piston therein, conduit means connecting to opposite sides of said piston working gas from said engine respectively of higher and lower working pressures to cause the piston to move, valve means respnsive to the piston as it nears the end of its movement for alternating the pressures on different sides of the piston causing it to oscillate, and said means pumping gas further comprising pumping structure connected to the piston and to said working chamber to pump working gas into said reservoir by oscillation of said piston, and valve means controlling the flow of working gas to said piston to control the pumping of working gas from said chamber.
 2. An engine as defined in claim 1 wherein said conduit means comprises two conduits with oppositely connected non-return valves coupled respectively therein, said conduits being connected between said working chamber and opposite sides of said free piston.
 3. An engine as defined in claim 2 wherein the valve means comprises a reversing valve coupled in said two conduits between said working chamber and said piston. 